Discussion in 'The Forge' started by cangooner, Oct 29, 2018.

  1. cangooner

    cangooner New Member

    Has anyone ever tried using 5160 (or similar) for razors? The reason I ask is that a colleague tore up the old dock at his family's cottage this summer, and brought me several hunks of mystery steel. Turns out part of it is wrought iron. :)

    Anyway, I was playing around with one of the pieces last night, and tried forge welding it to a piece of leaf spring. My intention was to make some knives, but now I'm thinking that looks like it has potential for a razor billet.

    But I can't recall hearing of anyone using 5160 for a razor... Possibly not hard enough?

    If not, no worries. I'd much rather source some proper steel than waste the wrought on something that won't work. It's pretty rare stuff around here.

    The piece pictured is around 1 1/4" x 5/16" x 5 1/2". I should have enough wrought to make three more billets like this one.

    32t likes this.
  2. Mike Blue

    Mike Blue Member

    Some time ago I was fortunate to work with Randy on the subject of optimal razor hardness. I was using a eutectic steel (1086V) but in this case each piece was hardened to a variety of Rc values between 57 and 63. Old razor pieces were tested and all over the map for hardness values. The harder pieces routinely had the same feedback from Randy, "Dammit, these blades are eating my stones." After all the testing, the optimum hardness turns out to be about Rc 59.5. If the chosen steel will get to Rc 59.5 or so, it will make a useful blade.

    The feedback loop is simple. Any well developed edge will cut hair. How long it cuts well, given acceptable edge development, depends on hardness. The Honemeister always has the final word about the process.

    5160 will easily heat treat to Rc 59. Go for it!
    cangooner, 32t, RezDog and 1 other person like this.
  3. cangooner

    cangooner New Member

    Awesome - thanks Mike!
  4. Bruno

    Bruno Administrator Staff Member

    One thing to always be wary of: spring steel can have fatigue cracks in it, that may not show up until you're forging it or grinding.
    So in terms of steel it is good steel, but any particular piece that has had a long life being used as a spring may have hidden defects that you don't see until you have put in several hours of work.

    Also keep in mind that heat treatment needs thinking about. If I see correctly, the edge is a piece of 5160, and the entire top is wrought.
    This means that during the quench, the edge is going to harden and the spine is going to contract upon cooling.
    As a result, there is going to be a lot of stress going to try and pull the 2 pieces apart. I've seen this happen so you need to think about ways to mitigate this.
    One of the things you definitely want to do is to make sure the toe of the razor has absolutely no faults in the weld, is polished perfectly smooth and rounded. Because if you leave a small line or crack in the point, there is a good chance you will have 2 pieces of razor.

    Any time you're using different types of steel, this is a consideration. Things like wrought are so different from high carbon steel that the differences will affect what you are doing.
    cangooner likes this.
  5. cangooner

    cangooner New Member

    Yeah, I'm a little worried about that join and what will happen in the quench. I'm toying with the idea of slapping some clay on the spine and, say, half the blade. Not to force a hamon (which I don't think 5160 is terribly good for anyway), but to ease the shock at the weld. Do you guys reckon that would help? I have a bunch of satanite for lining the forge, and was thinking of using that.

    At both ends of the billet there are spots where the weld doesn't look good. I'll try grinding that out, but am more or less resigned to losing an inch or so from each end.

    As for stress cracks, that shouldn't be a problem with this piece as it's actually new stock leaf spring. If I had salvaged it from an old vehicle, I don't think I would have used it for this piece. :)
  6. Bruno

    Bruno Administrator Staff Member

    I think it would be a very good idea to have the hardness boundary a good distance away from the weld indeed.
    That way, the stress boundary will be in the monosteel part, and not (so much) in the weld. I think that would significantly improve the chance of success.
    cangooner and Charlie Lewis like this.
  7. Mike Blue

    Mike Blue Member

    Correct on 5160, too much chrome to have a great hamon. Although in plain carbon steels, a carbon content around 0.61% is not only traditional but produces the best hamon.

    I'd bet the wrought iron won't move around much at all. There's not much carbon to have phase changes at the microcrystalline level to get movement. That does not mean the 5160 can't pull away from the wrought.

    Using a "clay" coat will delay cooling, and reduce the shock to the steel. But the idea of slowing down a process, that occurs at the speed of sound, By Hand, makes a smile appear in my day. Go for It.

    Get rid of the flaws and round off all the corners, all good. Mastery is really seeing a mistake before it happens, then not letting it happen.

    The rest is confidence.
    RezDog and cangooner like this.
  8. 32t

    32t Member

    A journeyman can cover his mistakes after they happen.

    And then there are the apprentices..........
    cangooner likes this.
  9. cangooner

    cangooner New Member

    And even worse than the bloody apprentices: the true amateurs like me! :)
  10. 32t

    32t Member

    I prefer this interpretation of amateur.

    a person who engages in a pursuit, especially a sport, on an unpaid basis.
    cangooner likes this.
  11. Bruno

    Bruno Administrator Staff Member

    I admit not knowing the contraction of wrought related to temeprature.
    My thinking was that, if the entire thing expands upon heating, and then the 5160 through hardens, it will stay expanded, and the wrought would pull back on it, keeping a tension there.

    In my mind it wouldn't be about slowing down the process, but about making an area between the hardened steel and the wrought, that would contract back again to pearlite. That way the weld would be under less tension. There would be tension in the 5160 itself where martensite meets pearlite, but since the stress would be in the monosteel part, there would be less likelihood of things tearing apart.
  12. Mike Blue

    Mike Blue Member

    5160 was formulated to be a fool-proof industrial steel. Factories were moving away from having workers who had to know how to heat treat metal objects. Or they were aging and being replaced by minimum wage types that the company was not going to expect to know such things. The material will through harden in thin enough sections. It can differential harden if the descent through temperature is controlled correctly or the thickness of the piece is enough. Essentially the old blacksmith hired originally knew something about steel. The new guy was told get it hot and just stick in in the oil bucket and no thought was required.

    Expansion and contraction are relative to the phase changes between face and body centered cubic arrangements in steel. E.g. iron plus carbon. Wrought iron should be mostly iron and silicates with not enough carbon to bring it up to steel-ish. Where the 5160 will undergo phase transformations because it's a hypoeutectic steel, the wrought probably won't. But then I don't know its heat history or exposure to time and temperature in a reducing atmosphere which could cause it to pick up carbon...it depends. Given the necessary welding heat to weld the wrought to the 5160, there will surely be carbon migration from the 5160 to the wrought portion but that depends on time at temperature. You need carbon in that weld boundary to lower the melting temperature enough to produce diffusion across the interface. That will produce an interesting visual effect at the weld boundary when all is said and done and the piece is etched. You can try this for yourself. Try welding two pieces of wrought iron together. The heat required alone is interesting enough. Failure is frequent in an ordinary shop.

    If the expansion/contraction of the 5160 was dynamic enough it could pull away from, or pull apart the wrought. Theoretically. It's unlikely in practical terms because the forging and/or welding temperatures of the 5160 are significantly lower than the temperatures needed for the wrought iron. At forging temperatures the wrought will be nicely plastic and move much easier under the hammer than the 5160 anyway, so the 5160 can dance around all it wants and the wrought follows. Once welded, there is no need to work the piece any higher than necessary for forging the 5160 by itself.

    Clay coating is about slowing down the process. Milliseconds maybe, but it's still a slowing. Delaying that rapid conversion to martensite, giving just that little bit of time longer to miss the nose of the isothermal curve is what it's all about.
    cangooner likes this.

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